This study will be done using pet dogs with naturally occurring nasal tumors. Radiotherapy, either alone or in combination with chemotherapy, is the standard of care for the treatment of nasopharyngeal tumors in humans and dogs. The ability to abrogate normal tissue toxicity without comprising tumor control and thereby increasing the therapeutic ratio is an important goal. The project has three specific aims focused on this goal. First is to document the treatment planning process, verify absorbed dose and document toxicity in the treatment dogs with naturally occurring tumors of the nasal and paranasal sinus region using helical tomotherapy. Second is to document conformal avoidance of normal critical tissue sin dogs with spontaneous tumors by exploiting the set-up verification and adaptive capabilities of helical tomotherapy. Acute and late effects secondary to irradiation using tomotherapy will be compared to normal tissue complications from standard megavoltage external beam radiotherapy of historical controls in the context of a phase II clinical trials. Our third aim is to demonstrate that the decrease in ocular toxicity afforded by helical tomotherapy will not be at the expense f patient survival time or local tumor control. To accomplish our goals we propose a phase II clinical trial of helical tomotherapy for the treatment of spontaneously occurring nasopharyngeal tumors in dogs. Acute and late effects secondary to irradiation will be the primary endpoints. Secondary endpoints in the phase II trial will be time to tumor progression and overall survival time.. The hypothesis is that the conformal avoidance and adaptive capabilities of helical tomotherapy will greatly reduce ocular toxicity associated with radiotherapy treatment of spontaneous nasal tumors in dogs without negative impact on tumor control. This study in a spontaneous tumor model in dogs will the first step to implementation of helical immunotherapy in human trials.